Bonsoir,
a = 5x +x² +30 + 6x
= x² +11x + 30
b = 4x²+12x -5x -15
= 4x² +7x -15
c = 4x -20 +x² -5x
= x² -x -20
d = 4x² -2x -14x +7
=4x² -16x +7
